Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Backfire through carb

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j_oetjens:
Any suggestions would be appreciated

I have a 1980 el camino I'm getting back fire through primaries when I floor it while parked in driveway and also when I drive and floor it. No backfire if I slowly accelerate in park or driving. When parked secondaries barely open at WOT. it has a rebuilt gm goodwrench performance 350. These are most of the specs:

Carburetor from 1975 Oldsmobile Cutlass 455
M4MC Rochester Quadrajet 7045183

Following cliffs book here are carb adjustments

Idle tubes 1.0mm / 0.0394
Idle down channel 1.5mm / 0.0591
Main air bleed main body 1.8mm / 0.071
Main air bleed air horn 1.8mm / 0.071
Lower idle air bleed main body 1.8mm / 0.071
No idle air bypass
Air horn milled
No choke
Primary 75 jets 45b rods
Hanger F 0.540
Secondary rods CV 0.0527
Secondary flaps tension spring set at 1/4 turn.
Idle mixture screws 3 turns out set at highest vacuum and highest rpm.
Base timing 18

Cliff Ruggles:
"B" series primary rods are incorrect for that unit.  I would get our 44 primary rods instead.

Team that up with the good accl pump from our SR kit, new secondary cam/spring and timed choke pull-off and I'll bet all those lean backfire issues disappear......Cliff

j_oetjens:
Thank you for the quick response Just to check the SR kit comes with accl pump and new cam/spring for secondary. I have 41j rods but got a lot of gas smell from exhaust. So I will get 44 rods. My choke pull off holds vacuum but vacuum from engine doesn't keep it fully pulled. Will the new choke pull  off be able to hold better 

Cliff Ruggles:
Yes the new pull-off will hold fine.  75 jets are huge in one of those units so not surprised it was stinky with 41 rods in it.....

j_oetjens:
Thank you will be ordering parts

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